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摘要
The production of heterogeneous sulfonic acid catalysts was carried out using an amine-catalyzed atomic layer deposition process utilizing 3-(mercaptopropyl)trimethoxysilane. The amine catalyst was employed to allow for low temperature deposition, since mercaptopropyl moieties undergo pyrolysis at similar to 200 degrees C. The highest loading achieved using alternating MPTMS and water pulses, with piperidine as the catalyst, was found to be comparable to loadings achieved by means of other classical synthesis techniques. The growth per cycle varied dramatically at different stages of the deposition, contrasting significantly from other known atomic layer deposition processes. Depositions using known amine catalysts, NH3 and pyridine, were compared to piperidine. NH3 was found to yield loadings comparable to piperidine only when higher NH3 partial pressures were used, while pyridine performed similarly to piperidine at the same partial pressures, but with a slower surface reaction rate. Depositions were monitored using a residual gas analyzer with the surface reaction directly measurable at low partial pressures of amine. Thermogravimetric analysis, Raman spectroscopy, Si-29, and C-13 CP/MAS NMR spectroscopy showed significant structural differences between the atomic layer-deposited and grafted materials. Mercaptopropyl groups attached to silica particles were oxidized to produce a sulfonic acid-functionalized mesoporous material. This catalyst was tested in the conversion of fructose to 5-(hydroxymethyl)furfural, giving a higher turnover frequency than a commercial catalyst.
- 出版日期2013-10-8
